1. Field of the Invention
The present invention concerns an inductive/MR composite type thin-film magnetic head which is integrally equipped with an inductive head used for writing and a magnetic resistance (MR) head used for read-out, and which can be used in recording and playback devices of various types of equipment such as computers and word processors, etc., e.g., in hard disk drives, etc. More specifically, the present invention concerns an inductive/MR composite type thin-film magnetic head which is designed so that magnetic recording can be performed at a high density exceeding 155 Mbit/cm.sup.2 (1000 Mbit/in.sup.2), and at a high data transmission rate exceeding 100 Mbit/sec.
2. Background Information
Recently, in order to deal with the increased density of magnetic recording and the reduced size and increased output of magnetic recording and playback devices, MR heads, which have a high playback sensitivity and in which the playback output does not depend on the relative speed with the recording medium, have been used for read-out purposes. Furthermore, composite type thin-film magnetic heads in which such an MR head is integrally combined with an inductive head used for writing, thus making it possible to reduce the track width and lower the impedance by reducing the number of coil turns, have also been employed. In conventional composite type thin-film magnetic heads, as is shown in for example FIGS. 1 and 2, an MR head 6 consisting of an MR element 5 which is sandwiched between a lower shield 3 and an upper shield 4 is formed on the surface of a substrate 1 consisting of a ceramic material, with an insulating film 2 being interposed between the MR head 6 and the substrate 1. An inductive head 12 which uses the aforementioned upper shield as a lower magnetic film, and in which a magnetic gap 7, organic insulating layers 8 and 9, a conductive coil 10 and an upper magnetic film 11 are laminated with the aforementioned lower magnetic film, is formed on top of the MR head 6.
The recording of signals on a recording medium 15 is accomplished by applying a square-wave writing current to the coil 10, thus generating a magnetic flux in the magnetic gap between the mutually facing tip end portions of the aforementioned upper and lower magnetic films, so that magnetization inversion regions known as magnetization transitions are formed with the timing of the plus and minus switching of the aforementioned current. Recorded signals are played back as follows: i.e., the magnetic flux from the recording medium 15, which passes through the MR element, varies with the timing at which the above-mentioned magnetization transitions pass through the area between the aforementioned upper and lower shields, thus causing a variation in the resistance of the MR element.
A writing head with a superior recording capacity is necessary in order to realize high-speed, high-density recording in such a composite type thin-film magnetic head. However, a lag component is generated in the writing current that flows through the coil of the inductive head as a result of the impedance of this coil; if this component becomes large, a distortion known as "blunting" is generated in the square wave of the writing current. Furthermore, an eddy current loss is generated in the yoke portions of the upper and lower magnetic films by the writing current flowing through the coil, and this further generates a delay in the high-frequency component of the magnetic field between the upper and lower magnetic poles. Accordingly, in cases where signals are written onto the recording medium at a high density, the adjacent magnetization transitions interfere with each other so that a non-linear shift of the writing position known as a non-linear transition shift (NLTS) is generated in the recording medium, and this increases the read-out error during playback of the signals.
In "Ko-Bs Poru Indakutibu/MR Heddo Fukugo Hakumaku Heddo" ("High-Bs Pole Inductive/MR Head Composite Thin-Film Head") by Hiroaki Kawashima et al. (Nippon Oyo Jiki Gakkai Gakujutsu Koen Gaiyoshu (1995) p. 221), a composite type thin film magnetic head is described in which NLTS is reduced by using a two-layer structure consisting of conventional NiFe and high-flux-density FeZrN in the tip end portion of the upper magnetic pole. As is clear from this description, the above-mentioned delay generated in the high-frequency component of the magnetic field between the upper and lower magnetic poles can easily be ameliorated if the material used to form the magnetic pole parts of the writing head is changed from the conventional NiFe (permalloy) to a material with a higher flux density, e.g., cobalt/zirconium/tantalum (CoZrTa, cobalt/niobium/tantalum (CoNbTa) or iron/zirconium/nitrogen (FeZrN).
However, in cases where the magnetic pole parts of an inductive head are formed using such high-flux-density materials, there is a danger of corrosion by water and acids, especially in cutting and washing processes used to cut respective chips from wafers and to form these chips into sliders. Accordingly, conventional thin-film magnetic head manufacturing processes cannot be used "as is." Furthermore, in order to achieve practicalization, there is a renewed demand for sufficient advance confirmation of the reliability of the writing head in cases where such a change of the magnetic pole material is made.